1. Field of the Invention
The present invention relates to a thermosensitive recording material. More particularly, the present invention relates to a thermosensitive recording material useful for a thermosensitive plotter for outputting a drawing prepared in a computer-aided design (CAD) system, and for a thermosensitive image-printer for outputting CRT images as a hard copy in a medical measurement.
2. Description of the Related Arts
It is known that a conventional thermosensitive recording material comprises a substrate material, for example, a paper sheet, synthetic paper sheet or plastic resin film, and a thermosensitive colored image-forming layer formed on a surface of the substrate material and comprising, as main components, a substantially colorless dye precursor consisting of, for example, an electron-donative leuco basis dye; a color-developing agent consisting of an electron-acceptive organic acid compound, for example, a phenolic compound; and a binder, and that the colored recording images can be created on the colored image-forming layer by reacting the dye precursor with the color-developing agent upon applying heat thereto.
This type of thermosensitive recording material is advantageous in that the recording apparatus can be made relatively compact and small size at a low cost, and can be easily maintained, and thus is widely utilized not only as a recording medium for facsimile machines and automatic ticket-vending machines, but also as an outputting medium for various printers and plotters of colored images of POS labels, CAD images and CRT medical images.
Also, it is known that a synthetic paper sheet having a multi-layer structure, and a bi-axially drawn thermoplastic resin film optionally containing an inorganic pigment, are utilized as a recording material that must have a high water-resistance and tensile strength, or as a recording material for a printer used with a CRT medical measurement apparatus that must record colored images with a high uniformity and resolving power, or as a recording material for a CAD plotter that must record colored images with a high dimensional stability and thin line images.
The conventional synthetic paper sheet having the multi-layered structure is produced by heat-kneading a polyolefin resin and a white inorganic pigment, extruding a melt of the resultant mixture through a film-forming die, drawing the resultant extruded sheet in a longitudinal direction thereof, laminating, on each of the two surfaces of the drawn sheet, one or two layers each consisting of a film formed from a mixture of a polyolefin resin with a white inorganic pigment and then drawing the resultant laminated sheet in a cross direction thereof.
The thermoplastic resin film is produced by extruding a melt of a thermoplastic resin comprising at least one member selected from, for example, polyolefin resins and polyester resins, through a film-forming die and then drawing the resultant extruded sheet biaxially, or by extruding a melt of a mixture of a thermoplastic resin with a white inorganic pigment through a film-forming die, and then drawing the resultant sheet biaxially.
Due to the above-mentioned processes, when a recording material consisting of a synthetic paper sheet with a multi-layer structure or the thermoplastic resin film is subjected to a thermosensitive recording procedure in which a thermal head is brought into contact with the recording material to record colored images at a high density, heat transmitted to a substrate material of the recording material causes the substrate material to be thermally shrunk and the recording material to be curled inward at the recorded face thereof, or to be cockled, and thus to exhibit an undesirable appearance.